1. Field of Invention
This invention relates to internal combustion engine operation and, in particular, to an automatic control system to prevent operation of the engine at excessive temperatures.
2. Brief Statement of the Prior Art
A common cause of damage and excessive wear of internal combustion engines results from excessive combustion temperatures in the engine. The operational temperature of the engine can repidly exceed a safe operational limit by improper operation where the engine is overloaded at any speed, requiring overthrottling and an excessive rate of fuel injection. This often occurs when driving a diesel powered vehicle into unnoticed head or side winds or climbing unnoticed grades, or failing to notice changes in ambient pressure resulting from altitude changes or high ambient temperatures. Additionally, malfunctions in the engine and its accessory equipment such as in the fuel supply system or fuel injectors, improper timing, turbocharger, restricted air cleaner, leak in a cross over tube, etc. can also cause an improper supply of fuel to the engine and result in a excessive operational temperature of the engine.
When the temperature of an engine exceeds a safe operational temperature, even for periods of relatively short duration, the damage that can be expected includes burned valves, head gasket failures, engine block distortion, cracked manifold and cylinder heads, burning and scoring of pistons, carbon deposits behind piston rings, piston ring failure with resultant high oil consumption and blow by, lubrication oil dilution, and cracks in the turbocharger unit.
It is generally recognized that the engine temperature of a diesel engine is critically affected by the aforementioned operational or equipment defects. As a result, many diesel engines are provided with pyrometers to monitor the exhaust gas temperature of the engine. Some of the pyrometers have been equipped with visual or audible warning signal generators to alert the operator when the exhaust gas temperature exceeds a predetermined, safe operational level. These devices are not entirely satisfactory since the warning signals can be inadvertently or deliberately ignored during operation of the engine. Since operations of relatively short durations at excessive temperatures can have disastrous effects on the engine, any failure to take corrective steps immediately upon indication of an excessive exhaust gas temperature, can result in an expensive and time consuming engine overhaul.